At present, people have driven vehicles instead of walking and there are an increasing number of vehicles on roads along with their improving living levels. Monitoring devices are typically arranged on the roads over which the vehicles are driven to monitor the vehicles are driven to monitor the vehicles on the roads, where the monitoring devices generally obtain images of license plates of the vehicles for an image recognition system to recognize characters of the license plates. A monitoring system obtains image information of characters including Chinese characters, digits, letters, etc., in an image of a license plate. Particularly a line in an image of a character will appear as a step structure when the line is in an inclined or curved status, like the characters 8 and B with step structures at their curved sections as illustrated in FIG. 1. Characters with similar appearances frequently occur in an obtained image of a license plate, for example, 8 and B, 0 and D, 7 and 1, 7 and T, D and Q, 2 and Z and other confusable characters.
As can be apparent from above, since characters with similar appearances may occur in an image of a license plate, the confusable characters in the image of the license plate will appear more similar when the license plate is inclined or smeared so that the image recognition system can not recognize the characters in the image of the license plate accurately. Consequently it is difficult to recognize an image of a confusable character in an image of a license plate in the prior art.